Chemistry Notes: Neutralization

Chemistry 2014-2015

When acids and bases react, the products most commonly formed are water and a salt (ionic compound). This is called a neutralization reaction.

Examples: HCl + KOH H2O + KCl

H2SO4 + 2 NaOH 2 H2O + Na2SO4

Acid-Base Reactions

What products would you get from the reaction of nitric acid and calcium hydroxide? Write the balanced equation for this reaction.   What is the name of the salt created in this reaction?

What products would you get from the reaction of potassium hydroxide and dichromic acid? Write the balanced equation for this reaction.   What is the name of the salt created in this reaction?

When an acid reacts with a base, the base often takes a proton (hydrogen ion) from the acid, which converts the acid to a base (called a conjugate base) and the base to an acid (called a conjugate acid).  

Conjugate Acid-Base Pairs

For example, when ammonia reacts with hydrochloric acid (shown above), the ammonia removes a proton from the hydrochloric acid. This results in the formation of an ammonium ion (the conjugate acid of ammonia) and a chloride ion (the conjugate base of hydrochloric acid).

Tip for identifying conjugate acid-base pairs—look at the last part of the formula (the anion). It is the same for both members of a conjugate acid-base pair.

For example, when water reacts with nitrous acid, it behaves as a base by removing a proton from nitrous acid. The conjugate base of nitrous acid is the nitrate ion, and the conjugate acid of water is H3O+, the hydronium ion.

HNO2 + H2O NO2- + H3O+

Water is an amphoteric substance—it can behave as an acid or a base.

On the other hand, when water reacts with ammonia, NH3, it behaves as an acid. The ammonia removes a proton from the water molecule. The conjugate base of water is the hydroxide ion, OH-, and the conjugate acid of ammonia is the ammonium ion, NH4

+.

NH3 + H2O NH4+ + OH-

Nitric acid reacts with ammonia according to the equation HNO3 + NH3 NH4

+ + NO3-

 What is the conjugate base of nitric acid?

What is the conjugate acid of ammonia?

Sulfuric acid reacts with lithium hydroxide according to the equation H2SO4 + 2 LiOH 2 H2O + Li2SO4

 What is the conjugate base of sulfuric acid?

What is the conjugate acid of lithium hydroxide?

Water reacts with phosphoric acid according to the equation H2O + H3PO4 H3O+ + H2PO4

-

 Does water act as an acid or a base in this reaction? What is the conjugate acid of water?

What is the conjugate base of phosphoric acid?